Theft-detector for electric meters.



J. T. SLOAN & A. G. ENGLISH.

THBPT DETECTOR TOR ELECTRIC METERS.

APPLICATION FILED AUG. 31, 1912.

'L Patented July 8,1913.

2 SHEETS-SHBET l.

IV] ZIV/55555 2 SHEETS'SHEET 2.

Patented July 8, 1913.

APPLICATION FILED AUC.C1,1C12.

J. T. SLOAN & A. G. ENGLISH.

THEFT DETECTOR TCR ELECTRIC METERS.

E6 D R7 .Re m6 JOHN T. SLOAN AND ARTHUR G. ENGLISH, OF WICI-I'ITA, KANSAS.

THEFT-DETECTOR FOR ELECTRIC METERS.

Specification of Letters Patent.

llatented July 8, 1913.

Application filed August 3.1, 1912. Serial No. 718,165.

To all whom t may concern:

Be it known that we, JOHN T. SLoAN and ARTHUR Gr. ENGLISH, citizens of the United States, residing at Wichita, in the county of Sedgwick and State of Kansas, have invented Certain new and useful improves ments inTheft-Detectors for Electric Meters,ofWhich the following is a specification.

rlthis invention relates to a device for detecting the theft of electric current in light power or other current supply systems where the attempted theft is by the employment of a shunt around the current coils of the electric meter between the supply and service circuits of the system.

One of the objects of the invention is the provision .of an attachment capable of use with meters of ordinary construction whereby a. shunt is established across the line wires whenever current is attempted to be stolen by shunting the meter, which shunt across .the line wires causes the fuses to be blown, resulting in `power to the service being cut ofi". The device is so constructed that it automatically restores itself when the fuses are replaced so that it is unneces sary for an attendant to Vvisit the meter attempted to be shunted for resetting the dctecting ldevice, which necessity is an objection to other types of detectors with which we lare acquainted.

Another object of the invention is the provision of a differential electro-magnet having its two windings, which are similar, connected respectively with the two sides of the circuit so that the magnetic flux 1s zero when the current on the ,ingoing and outgoing sides of the circuit are equal, and ass@ ciated with the electro-magnet is a shunt circuit containing a resistance and an electro-magnet that 1s energized` by the closing o f the .circuit when the di'erential electra magnet yis unbalanced, as by ,the meter being shunted upon an attempted theft of power. The .energizing of the electro-magnet in the shunt circuit establishes a shunt directly across the line wires to thereby cause the yfuses in the latter to be blown, thereby i1.terrupting the flow of current and preventing the attempted theft. The various tcircuit-closing.devices or contacts in the theft detector are so dlsposed that they gravitate to open-circuit position as soon as the line fuses blow, and consequently the de.- tector will be in condition for operation as soon as the line fuses are renewed.

With such objects in view and others, as will appear as the description. proceeds, the invention comprises the various novel features of construction `and arrangement of parts which will, be more fully described hereinafter and set forth with particularity in the claims ap ended hereto.

In the accomfiiinying drawings, Figure l is a perspective view of the attachment applied toa meter-,the casing of the latter being removed. Fig. 2 is `an interior View of .the detector. Fig. 3 isa detail view showing the connections between the terminals of the de tector and meter. F ig. 4 is a diagrammatic View 0f the circuit connections of the detector when the latter is in normal operation. Fig. 5 is a similar View showing the detector brought into operation and shunting the line wires.

Similar reference characters are employed to designate corresponding parts throughout the views.

lIn Fig. 1 of thc drawing, the theft detecting device is shown in connection with a well-known type of induction meter B, but it is to be understood `that Vthe detector attachment is not limited to any particular form .of electric meter. It will be observed that the attachment A is set up closely against the frame of the meter B, so that itl is impossible for the current coils of the i meter to he shunted by connecting a shunting wire with the appropriate terminals of the meter between the latter and the theft detector attachment.

The device comprises a lcasing 1 of any suitable construction and having 4a door 2 which is equipped with a seal 43, so that access to the .interior of the detector cannot be had without the broken seal serving as evidence. The'line wires 4 and 5 lead into the openings 6 and 7 in the left side of the casing 1 and connect with the electrical dcvices within the casing. y

The means ofconnecting the detector vand meter together are shown in Fig. 3, wherein 1 and 8 Yrepresent parts of the detector` casing and frame of .the meter, respectively.

lfor clamping the bars 15 and 16 in the meter terminals. Obviously, the terminal blocks will be of suitable insulating material. .I The theft detector comprises a dleren'tial electrounagnet C which has its-core suit-f ably fastened in the casing' 1, the said core havino an external member or limb 21 which extends downwardly to and beyond the lower end of the magnet C, which latter is shown in vertical position. On the lower end of the member 21 is an armature 22v that is disposed adjacent the polar extremity 23 of the core '20, sothat the armature will be attracted by thej latter, and, by engaging a iixed contact 24, close a shunt circuit including an electro-ma net hereinafter to be described. The ytwo windings 25 and 26 have their upper terminals connected, respectively, by wires 27 and 28gwith the terminal pieces 2,9 a-nd 30 to which the linewires 5 and 4 are connected, while the lower extremities of the'windings 25 and 26,v are connected with wires 31 and 32 4with terminals 12 and 11, respectively, which are connected with the meter terminals, as hereinbefore described.

Assuming current enters the attachment at the terminal 29 and leaves by the terminal 30, it is obvious that the total current will flow through the winding 25, in passing to the meter and through the winding 26 in leaving the meter, and as the windings are uniform in resistance and number of turns, the uxes due to both the windings will equally o pose each other so. that no attraction is pro uced onl the armature 22. -When, however, a shunt is established around the attachment and meter, as when the consumer attempts to steal current, there' will be, a greater flow of current through one Iwinding of the differentialelectro-magnet than through the other. This will unbal'ance the magnetic fluxes, due

- to the'windings, and consequently the armature 22 will be attracted and close a circuit which in turn establishes a shunt across the line wires. y y

The circuit established when the differential electro-magnet is unbalanced includesV an electro-magnet 33' fastened to a frame 34 secured in the casingl, and on this frame is pivoted an arm or lever 35 which carries an armature 36. Cne terminal of the magnet 33 is connected by a wire 37 with the fixed contact 24 of the main switch formed by suchfcontact and-the armature 22, and

the other terminal of the electro-magnet 33 is connected by a 'wire 381 witha resistance coil or element 39 which is in the form of a .wire mounted'on a suitable insulating base 40,v said coil being, in` turn, connected by a' wire 41 with the wire 27. The member 21 of the core of the differential electro-magnet the unbalancing'of the diierential magnet t C, current will flow from the line wire 5, through the wires 27 and 41, resista-nce 39, wire 38, electro-magnet 33, wire 37, Contact 24, armature 22, core member 21, bracket 43, wires 42 and 28. -The electro-magnet 33 thus becomes energized and attractsv its armature 36, which, in turn, closes a shunt directly across the line wires 4 and 5. This direct shunt consists of'wires 44 and 45 connectedwith the wires 27 and 28 that conneet, respectively, with a fixed cont-act 46 and a lever contact 47, which lever contact is fastened at one end to the armature 36 and carries at its other end a contact 48 adapted to engage the Contact 46. These, contacts 46 and l48 may be. made of carbon blocks or other suitable material so that theyy can carry the heavy flow of4 current when the direct or main shunt across the line wires is established. The lever 47 and armature 36' are so proportioned asto weight that when the'electro-magnet 33 becomes de'nerg'ized, the parts will gravitate to -a position where the contacts46 and 48 are separated, and furthermore'when the main electro-magnet C is denergized, the armature 22 will gravtate to open-circuit position. The establishing of the main shunt, by the contacts f 46 and 48 engaging each other, willv shunt the meter and the service circuit connected therewith, and as a result, the fuses in the main line will be blown. thus interrupted so that the parts of the detector will return to normal position and be ready for operation when another attempt is madeto steal current.' After the/ station attendant restores the fuses, the supply system is again ready for use, without the necessity of the meterman visiting the meter for restoring the attachment which has automatically restored itself.

From theoregoing description, taken in connectionk Jwit-h the accompanying drawings,the advantages of the construction and of the .methody of operation willi be readily apparent to thOSeskilIed in the Iart to which the invention appertains, and while we have' described the principle of operation of the invention, together with the apparatus which we consider to be the ,t lbest embodiment thereof, we desire to lhave it understood that the apparatus shown is merely illustrative, and that such changes may be The current is made when desired as are within thescope of the claims appended hereto.-

Having thus described the invention, what we claim as new, is:-

1. The combination of main wires, and a meter connected therewith, with a theft detecting device for the meter, said device comprising means responsive to a greater flow of current on one side of the circuit of 'the meter than on the opposite side, and

means for establishing a shunt across the main wires when the said device responds to said dilerence of current flow.

2. The combination of a meter and supply mains connected therewith, with a ,theft detecting device associated with the meter, said device comprising a differentiallywound electro-magnet having its coils connected respectively with said mains and terminals of the meter, means for establishing a shunt across the mains, and means controlling the shunt-establishing means by the energizin of the electro-ma et 4when the current ow through one winding of the latter is dierent from the current How in the other winding.

3. The combination of a meter, and. mains leading thereto, with a theft detector comprising dierential electro-magnetic means adapted to become operative when the current on one side of the circuit exceeds the current on the other side, a second electromagnet, means controlled by the first electro-magnet for closing the circuit of the second electro-magnet, and means controlled by the second electro-magnet for establishing a shunt across the mains.

4. The combination of a meter, supply mains leadingthereto, and a theft detecting4 device comprising electro-magnetic means composed of two windings connected with the said mains and the terminals of the meter and adapted under normal conditions to produce equally-opposing fluxes, a main switch adapted to be closed by the electromagnet when the said fluxes vary with respect to each other, means energized by the closin of the said switch, and means for establlshing a short circuit across the Supply mains by the energizing of the last-mentioned means. p

5. The combination of a meter, and supply mains therefor, with a theft detecting device comprising electro-magnetic means having opposed windings connected respectively with the supply mains and terminals of the meter, a swltch controlled by the said meansand connected with one of the mains, a resistance connected with the other main, an electro-magnet in circuit with the switch and with the resistance, and a shunt adapted to be closed by the energizing of the electromagnet to short-circuit the supply mains.

Intestimony whereof we aflx our signatures in presence of two witnesses.

JOHN T. SLOAN. ARTHUR G. ENGLISH. Witnesses:

C. B. TINGLEY, W. O. EDMoNDs. 

